Centrifugal compressor

ABSTRACT

A centrifugal compressor is able to cause air to efficiently flow to an impeller thereof, and enables improvement of operating efficiency. The centrifugal compressor has: a casing having an inlet flow channel and a connection flow channel formed therein, the inlet flow channel having a suction port provided at one place thereof, the connection flow channel being connected to the inlet flow channel; a main shaft inserted in the casing; an impeller fixed to the main shaft and arranged in the inlet flow channel; and an inlet guide vane unit having a plurality of inlet guide vanes arranged upstream of the impeller of the inlet flow channel. In the inlet guide vane unit, an arrangement interval between inlet guide vanes at a suction port side is narrower than an arrangement interval of inlet guide vanes at a side opposite to the suction port side.

TECHNICAL FIELD

One or more embodiments of the present invention relate to a centrifugalcompressor having: inlet guide vanes; and a suction port at one placethereof.

BACKGROUND

Centrifugal compressors are used in turbo freezing machines,petrochemical plants, natural gas plants, and the like. In a centrifugalcompressor, pressure increase due to centrifugal force is obtained bykinetic energy being given to a fluid by rotation of an impeller and thefluid being blown outward in a radial direction. Disclosed in PatentLiterature 1 is a turbo charger (supercharger), which is one type ofcentrifugal compressors, and includes inlet guide vanes that straightenair that flows to an upstream side of an impeller (blades forcompressor) and that adjust the amount of the air flowing therein (seePatent Literature 1).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Unexamined Patent Application    Publication No. 2010-71140 A

SUMMARY

By the angle of the inlet guide vanes with respect to the impeller, thatis, the opening, being made variable, and resistance in the flow channelbeing made changeable; the amount of air flowing therein is able to beadjusted. Further, in some centrifugal compressors, the inlet guidevanes are fixed. Centrifugal compressors have, in the rotating directionof the main shafts, distribution in the amount of fluid that flows tothe impellers, and when the difference in the flow rate is increased,operating efficiency of centrifugal compressors is reduced.

One or more embodiments of the present invention may provide acentrifugal compressor that is able to cause air to efficiently flow toan impeller thereof, and enable improvement of operating efficiency.

A centrifugal compressor according to one or more embodiments of thepresent invention may include a casing having an inlet flow channel anda connection flow channel formed therein, the inlet flow channel havinga suction port provided at one place thereof, the connection flowchannel being connected to the inlet flow channel, a main shaft insertedin the casing, an impeller fixed to the main shaft, and arranged in theinlet flow channel, and an inlet guide vane unit having plural inletguide vanes arranged upstream of the impeller of the inlet flow channel.In the inlet guide vane unit, an arrangement interval between the inletguide vanes at the suction port side is narrower than an arrangementinterval between the inlet guide vanes at a side opposite to the suctionport side.

Here, it may be that in the inlet guide vane unit, arrangement intervalsamong a first group of the inlet guide vanes that are at an end portionside at the suction port side and that are 25% of all of the inlet guidevanes are narrower than arrangement intervals among a second group ofthe inlet guide vanes that are at an end portion side opposite to thesuction port and that are 25% of all of the inlet guide vanes.

Further, it may be that in the inlet guide vane unit, a relation betweena maximum value dmax and a minimum value dmin of intervals between theinlet guide vanes is expressed as 0.6≦dmin/dmax<1.0.

Further, it may be that in the inlet guide vane unit, intervals betweenthe inlet guide vanes change, with reference to a reference line of asine function along a rotating direction of the main shaft, in a rangeof equal to or less than 20% of amplitude of the reference line.

Further, it may be that in the inlet guide vane unit, a position wherethe interval between the inlet guide vanes is the widest is at aposition moved to an upstream side in the rotating direction of the mainshaft from an end portion opposite to the suction port by an anglelarger than 0° and equal to or less than 40°.

Advantageous Effects of Invention

According to one or more embodiments of the present invention, byarrangement intervals of inlet guide vanes being changed according topositions thereof, circumferential direction distribution of a fluidflowing to an impeller is able to be equalized, and operating efficiencyis able to be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a schematic configuration of a compressoraccording to one or more embodiments.

FIG. 2 is a sectional view along a line A-A of FIG. 1.

FIG. 3 is a partial enlarged view of an inlet guide vane unit.

FIG. 4 is a graph illustrating an example of distribution of flow rateof a fluid flowing therein.

FIG. 5 is a graph illustrating an example of a relation betweenpositions and intervals of inlet guide vanes.

FIG. 6 is a schematic diagram illustrating an example of the inlet guidevanes.

FIG. 7 is a graph illustrating an example of a relation betweenpositions and intervals of inlet guide vanes.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one or more embodiments according to the present inventionwill be described in detail, based on the drawings. The invention is notlimited by this these embodiments. Further, components in one or moreembodiments described below include any component easily substitutableby those skilled in the art or any component that is substantially thesame. A compressor 1 may be used as an apparatus that suppliescompressed air to a freezing machine, a petrochemical plant, a naturalgas plant, or the like.

As illustrated in FIG. 1, the compressor (centrifugal compressor) 1 ofone or more embodiments is a multistage compression type centrifugalcompressor. In one or more embodiments, the compressor 1 will bedescribed as a multistage compression type compressor, but thecompressor 1 may be a single stage compression type compressor instead.The compressor 1 has a casing 2, a drive unit 4, a main shaft 6, and acompression unit 14.

The casing 2 is a housing, and has the drive unit 4, the main shaft 6,and the compression unit 14 accommodated therein. The casing 2 has aflow channel, through which a fluid to be compressed, which is air inone or more embodiments, flows, formed therein. The casing 2 has anopening at an upstream end of the flow channel, through which air flows,the opening serving as a suction port 12, and another opening at adownstream end of the flow channel, through which air flows, this latteropening serving as a discharge port 16. The compressor 1 of one or moreembodiments has one suction port 12. In the casing 2, a flow channel forair, between the suction port 12 and the compression unit 14, serves asa suction flow channel 102. In the casing 2, a flow channel for air,between the discharge port 16 and the compression unit 14, serves as adischarge flow channel 104. In the compressor 1, the suction flowchannel 102 is arranged in a direction inclined with respect to an axialdirection of the main shaft 6, which is, in one or more embodiments, ina direction orthogonal to the axial direction of the main shaft 6.

The drive unit 4 has an electric motor and a power transmission unit.The drive unit 4 rotates the main shaft 6, by transmitting output of theelectric motor through the power transmission unit to the main shaft 6.The main shaft 6 is inserted in the casing 2, and rotatably supportedwith respect to the casing 2. The main shaft 6 is rotated by the driveunit 4. A rotation unit of the compression unit 14 is fixed to the mainshaft 6.

The compression unit 14 is arranged in the casing 2, compresses airflowing therein from the suction port 12, and discharges the compressedair from the discharge port 16. The compression unit 14 has compressionunits 18 a, 18 b, 18 c, and 18 d. The compression units 18 a, 18 b, 18c, and 18 d are arranged between the suction flow channel 102 and thedischarge flow channel 104, in this order. The compression unit 18 a isconnected to the suction flow channel 102. The compression unit 18 d isconnected to the discharge flow channel 104. Since the compression units18 a, 18 b, 18 c, and 18 d are similarly formed except for only theirarrangement positions, the compression unit 18 a will be described as anexample.

The compression unit 18 a has a flow channel, which is formed, by thecasing 2, so as to discharge a fluid after sucking in and compressingthe fluid. The flow channel of the compression unit 18 a has an inletflow channel 33, and a return channel 35. An upstream side of the inletflow channel 33 is connected to the suction flow channel 102, and adownstream side of the inlet flow channel 33 is connected to the returnchannel 35. A downstream side of the return channel 35 is connected toan inlet flow channel 33 of the compression unit 18 b of the next stage.The compression unit 18 a has an impeller 32 provided in the inlet flowchannel 33, and a return vane 34 provided in the return channel 35. Theimpeller 32 is fixed to the main shaft 6. The impeller 32 has manyblades 32 a arranged on a surface thereof. The impeller 32 sends airthat flows into the inlet flow channel 33 towards the return channel 35,by rotating together with the main shaft 6. With a downstream side ofthe impeller 32 serving as a diffuser, the inlet flow channel 33decelerates the fluid that has been accelerated by the impeller 32, andraises pressure of the fluid. The return vane 34 is arranged in thereturn channel 35. The return vane 34 straightens the fluid flowing inthe return channel 35. The fluid that has passed the return channel 35flows into the compression unit 18 b.

In the compressor 1, the main shaft 6 of the compression unit 14 rotatesvia the power transmission unit by drive of the electric motor of thedrive unit 4. The impeller 32 then rotates together with the main shaft6. Thereby, a fluid: is sucked in from the suction port 12; flows intothe suction flow channel 102; flows into the inlet flow channel 33 ofthe compression unit 18 a via an inlet guide vane unit 100; and isaccelerated by the impeller 32, and thereafter, kinetic energy isconverted to internal energy by the diffuser. Further, the fluid isturned back to the inlet flow channel 33 of the compression unit 18 b bythe return channel 35, and is accelerated by the impeller 32, andthereafter, kinetic energy is converted to internal energy by adiffuser. In the compressor 1, after being similarly compressed in thecompression units 18 c and 18 d, the fluid is discharged from thedischarge port 16 of the discharge flow channel 104.

Next, in addition to FIG. 1, by use of FIG. 2 to FIG. 3, the inlet guidevane unit (IGV, or guiding guide vanes) 100 will be described. FIG. 2 isa sectional view along a line A-A of FIG. 1. FIG. 3 is a partialenlarged view of the inlet guide vane unit.

The inlet guide vane unit 100 is, as described above, in a flowingdirection of the fluid, arranged in a flow channel upstream of theimpeller 32 of the compression unit 18 a, which is arranged mostupstream in the flowing direction of the fluid. The inlet guide vaneunit 100 has plural inlet guide vanes 101. The plural inlet guide vanes101 are arranged over the entire circumference of the main shaft 6, atpredetermined intervals in a rotating direction of the main shaft 6, asillustrated in FIG. 2. That is, an inlet guide vane 101 is arranged at adistance from an inlet guide vane 101 adjacent thereto in the rotatingdirection (circumferential direction) of the main shaft 6. The inletguide vanes 101 are each a plate like member extending in a radialdirection of the main shaft 6. Depending on their positions in therotating direction, the inlet guide vanes 101 are shaped differently,and their surfaces at the suction port 12 side are curved surfacesconvexed to a side opposite to the suction port 12 so as to guide theair flowing therein from the suction port 12 to the center side of themain shaft 6. The air that has flown in from the suction port 12 passesbetween the inlet guide vanes 101 and advances to a position, at whichthe impeller 32 of the inlet flow channel 33 is arranged.

In the inlet guide vane unit 100, when an interval between the inletguide vanes 101 is d, this interval changes depending on the position inthe rotating direction of the main shaft 6. The interval d is, asillustrated in FIG. 3, a diameter of the smallest circle that joins endportions of two adjacent inlet guide vanes 101, the end portions beingat the center side of the main shaft 6. In the inlet guide vane unit100, an interval between the inlet guide vanes 101 of a suction portside end portion 120 is narrower than an interval between the inletguide vanes 101 of a terminal side end portion 122. The suction portside end portion 120 is a position nearest to the suction port 12 alonga rotating direction R of the main shaft 6. The terminal side endportion 122 is a position nearest to a terminal 112 along the rotatingdirection R of the main shaft 6. The terminal 112 is a position oppositeto the suction port 12 in the flowing direction of the air in thesuction flow channel 102, and is a position rotated by 180 degrees fromthe suction port side end portion 120 in the rotating direction R. Inone or more embodiments, the terminal side end portion 122 is 0 degrees,and the angle that increases as rotated in the rotating direction R(circumferential direction position) is 8.

FIG. 4 is a graph illustrating an example of distribution of flow rateof a fluid flowing therein. FIG. 4 is measurement results of weight flowrate of air (air that has passed the inlet guide vanes 101) that flowsinto the inlet flow channel 33 of the compressor 1 according to one ormore embodiments, in which the interval between the inlet guide vanes101 of the suction port side end portion 120 has been made narrower thanthe interval between the inlet guide vanes 101 of the terminal side endportion 122. A comparative example is measurement results of weight flowrate when intervals between inlet guide vanes 101 are made constantalong the rotating direction R. By the interval between the inlet guidevanes 101 of the suction port side end portion 120 being made narrowerthan the interval between the inlet guide vanes 101 of the terminal sideend portion 122, through adjustment of the intervals between the inletguide vanes 101 according to their positions; even if the compressor 1has a suction port at one place and is configured such that air flows inonly from a part of the circumferential direction, as illustrated inFIG. 4, the weight flow rate of the air at positions (circumferentialdirection positions) along the rotating direction R is able to beequalized. Specifically, by adjustment of the intervals between theinlet guide vanes 101, the weight flow rate of air is able to be moreequalized than when the intervals are made constant. The inlet guidevane unit 100 is able to supply air to the impeller 32 evenly.

In the inlet guide vane unit 100, arrangement intervals among a firstgroup 130 of inlet guide vanes 101 at the suction port side end portion120 side, the first group 130 being 25% of all the inlet guide vanes101, are possibly narrower than arrangement intervals among a secondgroup 132 of inlet guide vanes 101 at the terminal side end portion 122side, the second group 132 being 25% of all the inlet guide vanes 101.If the number of inlet guide vanes 101 that are 25% of all of the inletguide vanes 101 includes a decimal point, the numerical value is roundedup. In the inlet guide vane unit 100, by the arrangement intervals ofthe first group 130 being made narrower than the arrangement intervalsof the second group 132, the weight flow rate of air is able to beequalized. The inlet guide vane unit 100 is able to supply air to theimpeller 32 evenly.

Further, in the above description, the intervals of the inlet guidevanes 101 that are 25% of the total number of inlet guide vanes 101arranged at each of the suction port side end portion 120 side and theterminal side end portion 122 side are compared with each other, butlimitation is not made thereto. In the inlet guide vane unit 100,intervals between inlet guide vanes included in a range of 45 degreesbefore and after a base point, which is the suction port side endportion 120, that is, in a range of 90°, may be made narrower thanintervals of inlet guide vanes 101 included in a range of 45° before andafter a base point, which is the terminal side end portion 122, that is,in a range of 90°. By the intervals between the inlet guide vanes 101included in the ranges that are set based on the angles satisfying theabove relation as described above, air is able to be supplied evenly.

Further, it may be that the intervals between the inlet guide vanes 101are changed gradually in the rotating direction, but inlet guide vanes101 arranged at equal intervals may be included.

In the inlet guide vane unit 100, a maximum value dmax, and a minimumvalue dmin, of the intervals between the inlet guide vanes 101 possiblysatisfy a relation, “0.6≦dmin/dmax<1.0”. By the difference between thearrangement intervals being kept in the above range, the weight flowrate of air is able to be equalized more infallibly.

In the inlet guide vane unit 100, it is possible that the intervalsbetween the inlet guide vanes 101 are changed gradually in the rotatingdirection R. Specifically, of one round in the rotating direction R,possibly: a half round (corresponding to an angle range of 180°) is anincreasing region; and a half round (corresponding to an angle range of180°) is a decreasing region.

FIG. 5 is a graph illustrating an example of a relation betweenpositions and intervals of inlet guide vanes. In the inlet guide vaneunit 100 illustrated in FIG. 5: 360 degrees of one round is one cycle;and based on a sine function, in which the interval becomes maximum whenθ is 0° at the terminal side end portion and the interval becomesminimum when θ is −180° and 180° at the suction port side end portion120, the intervals between the inlet guide vanes 101 are increased anddecreased. As illustrated in FIG. 5, by the intervals between the inletguide vanes 101 being increased and decreased based on the sinefunction, the flow rate is able to be made more even. Further, when theintervals are changed with the sine function, the difference between themaximum value and the minimum value may be in the above described range.

The intervals between the inlet guide vanes may be changed based onpoints on the sine function, based on the sine function, but limitationis not made thereto. In the inlet guide vane unit, the intervals betweenthe inlet guide vanes may be changed, with reference to a reference lineof the sine function along the rotating direction of the main shaft, ina range of 20% or less of the amplitude of the reference line. That is,the intervals between the inlet guide vanes may be deviated in a certainrange from points on the sine function. For example, the intervals maybe changed stepwisely, by intervals between plural inlet guide vanesbeing made the same. Accordingly, by the intervals between the inletguide vanes being changed, with reference to the reference line of thesine function, in the range of 20% or less of the amplitude of thereference line; the weight flow rate of air is also able to be equalizedin the rotating direction. Further, in the inlet guide vane unit, with areference line of a sine function along the rotating direction of themain shaft being a reference, intervals between inlet guide vanes may bechanged in a range of 5% or less of the amplitude of the reference line,and the intervals between the inlet guide vanes may be changed in arange of 5% or less of the amplitude of the reference line.

FIG. 6 is a schematic diagram illustrating an example of the inlet guidevanes. Further, as illustrated in FIG. 6, an angle θa formed between: aline extended from an end portion of a pressure surface 140, which is asurface of the inlet guide vane 101, the surface being at the suctionflow channel 102 side, the end portion being at a center 142 side of themain shaft 6; and a line joining the end portion and the center 142, maybe equal to or larger than 0° and equal to or less than 10°.Accordingly, the formed angle θa becomes positive in a directionopposite to the rotating direction, with a center side end portion ofthe inlet guide vane 101 being the center. By the pressure surface 140of the inlet guide vane 101 having the shape satisfying the abovedescribed range, the straightening effect is able to be improved more.

FIG. 7 is a graph illustrating an example of a relation betweenpositions and intervals of inlet guide vanes. In the example illustratedin FIG. 5, when θ is 0°, the interval between the inlet guide vanesbecomes maximum, and when θ is 180°, the interval becomes minimum, butlimitation is not made thereto. As illustrated with a second pattern inFIG. 7, a position in the inlet guide vane unit 100, the position beingwhere the interval between the inlet guide vanes 101 is the widest, maybe at a position moved from the terminal side end portion 122 to theupstream side in the rotating direction of the main shaft by an anglelarger than 0° and equal to or less than 40°. That is, an amount ofdeviation 160 illustrated in FIG. 7, from a first pattern in FIG. 5, maybe made larger than 0° and equal to or less than 40 degrees to theupstream side in the rotating direction. Accordingly, by the positionwhere the interval between the inlet guide vanes 101 is the widest beingdeviated to the upstream side in the rotating direction, the weight flowrate is able to be adjusted in consideration of influence of theimpeller, and the weight flow rate of air is able to be equalized alongthe rotating direction. As to the intervals between the inlet guidevanes, similarly to the position where the interval between the inletguide vanes 101 is the widest, the position where the interval betweenthe inlet guide vanes 101 is the narrowest may be deviated to theupstream side in the rotating direction, and may be at a position movedfrom the suction port side end portion 120 to the upstream side in therotating direction of the main shaft by an angle larger than 0° andequal to or less than 40°.

Although the disclosure has been described with respect to only alimited number of embodiments, those skilled in the art, having benefitof this disclosure, will appreciate that various other embodiments maybe devised without departing from the scope of the present invention.Accordingly, the scope of the invention should be limited only by theattached claims.

REFERENCE SIGNS LIST

-   -   1 COMPRESSOR    -   2 CASING    -   4 DRIVE UNIT    -   6 MAIN SHAFT    -   12 SUCTION PORT    -   14 COMPRESSION UNIT    -   16 DISCHARGE PORT    -   18 a, 18 b, 18 c, 18 d COMPRESSION UNIT    -   32 IMPELLER    -   32 a BLADE    -   33 INLET FLOW CHANNEL    -   34 RETURN VANE    -   35 RETURN CHANNEL    -   100 INLET GUIDE VANE UNIT    -   101 INLET GUIDE VANE    -   102 SUCTION FLOW CHANNEL    -   104 DISCHARGE FLOW CHANNEL    -   120 SUCTION PORT SIDE END PORTION    -   122 TERMINAL SIDE END PORTION    -   130 FIRST GROUP    -   132 SECOND GROUP    -   160 AMOUNT OF DEVIATION

1. A centrifugal compressor, comprising: a casing having an inlet flowchannel and a connection flow channel formed therein, the inlet flowchannel having a suction port provided at one place thereof, theconnection flow channel being connected to the inlet flow channel, amain shaft inserted in the casing; an impeller fixed to the main shaft,and arranged in the inlet flow channel; and an inlet guide vane unithaving a plurality of inlet guide vanes arranged upstream of theimpeller of the inlet flow channel, wherein in the inlet guide vaneunit, an arrangement interval between the inlet guide vanes at thesuction port side is narrower than an arrangement interval between theinlet guide vanes at a side opposite to the suction port side.
 2. Thecentrifugal compressor according to claim 1, wherein in the inlet guidevane unit, arrangement intervals among a first group of the inlet guidevanes that are at an end portion side at the suction port side and thatare 25% of all of the inlet guide vanes are narrower than arrangementintervals among a second group of the inlet guide vanes that are at anend portion side opposite to the suction port and that are 25% of all ofthe inlet guide vanes.
 3. The centrifugal compressor according to claim1, wherein in the inlet guide vane unit, a relation between a maximumvalue dmax and a minimum value dmin of intervals between the inlet guidevanes is expressed as 0.6≦dmin/dmax<1.0.
 4. The centrifugal compressoraccording to claim 1, wherein in the inlet guide vane unit, intervalsbetween the inlet guide vanes change, with reference to a reference lineof a sine function along a rotating direction of the main shaft, in arange of equal to or less than 20% of amplitude of the reference line.5. The centrifugal compressor according to claim 4, wherein in the inletguide vane unit, a position where the interval between the inlet guidevanes is the widest is at a position moved to an upstream side in therotating direction of the main shaft from an end portion opposite to thesuction port by an angle larger than 0° and equal to or less than 40°.